Retention catheter

ABSTRACT

Disclosed is a retention catheter of the Foley type and a method of manufacturing such a catheter. The catheter is comprised of an extruded tube with a funnel at one end and, at the other end, a closed end sleeve peripherally bonded to the tube and having a substantially solid tip. The method of manufacture includes the step of radially compressing the tube and sleeve while bonding.

nited States atent 11 1 Gilbert et al.

RETENTION CATHETER Inventors: John W. Gilbert, Greenwich;

Ahmed Panagrossi, North Haven, both of Conn.

International Paper Company, New York, NY.

Filed: Apr. 5, 1973 Appl. No.: 347,996

Assignee:

US. Cl. 128/349 B, 29/481 Int. Cl A6lm 25/02 Field of Search 29/481; 128/349 B, 349 BV References Cited UNITED STATES PATENTS Harautuneian 128/349 B [451 May 28, 1974' 3,495,594 2/1970 Swanson 128/349 B 3,528,869 9/1970 Dereniuk 3,547,126 12/1970 Birtwell 3,746,003 7/1973 Blake et al. 128/349 B Primary Examiner-Channing L. Pace Attorney, Agent, or Firm-Alfred L. Michaelsen [57] ABSTRACT Disclosed is a retention catheter of the Foley type and a method of manufacturing such a catheter. The catheter is comprised of an extruded tube with a funnel at one end and, at the other end, a closed end sleeve peripherally bonded to the tube and having a substantially solid tip. The method of manufacture includes the step of radially compressing the tube and sleeve while bonding.

18 Claims, 8 Drawing Figures 1 RETENTION CATHETER BACKGROUND OF THE INVENTION 1. Field to Which the Invention Pertains Well known to physicians is the fact that individuals may, for a variety of reasons, lose control of their urinary fucntion. Although the reasons for the loss of urinary control are manifold, the consequent treatment is a rather well accepted medical practice which involves inserting a tube or catheter up the urinary passage until the remote or distal end is located within the bladder. The near or proximal end of the catheter remains outside of the body and there is thus provided a path or means through which the bladder may drain. Once a catheter has been passed through the urinary tract and inserted into the bladder, it is generally both medically desirable and necessary to have the catheter retained in the urinary tract with the distal end of the catheter positioned within the bladder. Catheters which are designed for such a function are called urinary retention catheters and are generally provided with some means to promote retention. Typically, this retention capability is provided by including an inflatable balloon at the distal end of the catheter. During insertion, the balloon is deflated. After the distal end of the catheter is positioned within the bladder, the balloon is inflated bypassing a fluid, typically water, through a passage within the catheter which is referred to as an inflation lumen. When the balloon is inflated, the inflation lumen is sealed and the inflated balloon within the bladder insures retention. Thereafter, the bladder may drain through a second passage within the catheter, i.e. the drainage lumen.

There are a number of medical procedures which involve the use of catheters and, as a result, catheters are generally referred to by a name associated with their function, e.g. urinary catheters, tracheal catheters, venous catheters, etc. While all such catheters must be fabricated so as to insure the safety and comfort of the patient, the physiological demands imposed upon a urinary retention catheter are particularly severe and appear to result in conflicting design criteria. For example, the comfort of the patient dictates that a urinary retention catheter be as soft and as flexible as possible. On the other hand, from a structural point of view, such a catheter must be sufficiently rigid to insure that as it traverses the urinary tract, the catheter tube will not bend to an extent which results in occluding or reducing the size of the drainage lumen and the inflation lumen. Similarly, it is clearly desirable that the outer diameter of the catheter be as small as possible while the diameter of the drainage lumen be as large as possible. However, the maximum outer diameter of the catheter is substantially defined by the diameter of the urinary tract and the comfort of the'patient while the contractive forces which are exerted on the catheter by the urinary tract substantially define a minimum wall thickness between the drainage lumen and the exterior of the catheter.

Of substantial concern to both the patient and the physician is the balloon and its proper inflation. After the catheter is inserted, it is desirable that the balloon be so constructed and arranged that it can be inflated with a minimum inflation pressure. Such an objective is desirable because the maximum inflation pressure required to inflate a balloon will be the determining factor with respect to the minimum wall thickness surrounding the inflation lumen. Since one desires to maximize the size of the drainage lumen and since the area occupied by the inflation lumen diminishes the size of the drainage lumen, it follows that one wishes to utilize a minimum wall thickness for the inflation lumen and, therefore, the balloon construction should be such as to require a minimum pressure for inflation. While one may construct a urinary retention catheter having a balloon which will inflate with a minimum pressure, the resulting structure may, and often does, possess undesirable features. For example, to achieve a low inflation pressure, a soft and pliant material may be used for the balloon. However, from a manufacturing point of view, it is generally most economical to fabricate the balloon as an integral part of the catheter tip and, thus, the catheter tip will also be soft and pliant. Constructions of this type, which are known to the prior art, unfortunately possess certain disadvantages which are discussed hereinafter.

Finally, urinary retention catheters must not only meet or exceed the various medical and patient oriented criteria discussed above but, in addition, such a catheter must be of a construction which lends itself to a method of high volume, low cost manufacture. Such manufacturing criteria are particularly significant with respect to urinary retention catheters since tolerances are critical yet the cost of the resulting product must be consonant with the disposable nature of the product.

The invention disclosed herein relates to a novel urinary retention catheter and the method of manufacturing such a catheter.

2. Prior Art In an attempt to satisfy the various and conflicting criteria heretofore discussed, the prior art reflects an evolution of catheter designs. For several decades, all urinary retention catheters were manufactured by a dipping process wherein two longitudinally adjacent wires were dipped in a latex bath until a catheter tube of the desired diameter was built up. Subsequently a hole was pierced through the wall of the tube at one end and communicated with the cavity formed by one of the two wires, which cavity would later be the inflation lumen. Thereafter, a release agent was deposited around the tube in the area of the hole and the end of the tube was again dipped to build up another layer of latex at the end of the tube and which would constitute the balloon.

The catheter which resulted from this method of manufacture was widely accepted. However, certain disadvantages of the catheter construction by this method of manufacture have been recognized. One disadvantage arises from the dipping process whereby precise dimensional control of the catheter diameter tends to be problemsome which, in turn, tends to increase th manufacturing cost.

While the strength and elasticity of latex rubber renders that material ideal as catheter material, it has been found that, as do most materials, it possesses a degree of susceptibility to encrustation from the salts commonly found in urine. On the other hand, recent developments in materials technology have made available the silicone rubbers which promise to be relatively free of susceptibility to encrustation.

Thus, more recent prior art catheter constructions have embodied silicone rubber tubes for the tip and body to relieve the encrustation problemand to enjoy a further advantage of compatibility with human tissue. Although the prior art has established that silicone rubber is an acceptable material for a catheter, the problem still remains as to the structure of the catheter and the method of manufacturing a particular structure. The problems associated with prior art silicone rubber catheter constructions is exemplified by the catheter construction disclosed by Birtwell in US. Pat. No. 3,547,126. The Birtwell construction employs an extruded silicone tube as the body of the catheter in combination with a molded silicone tip which is provided with a rearwardly extending portion. The rearwardly extending portion is attached to the catheter tube or body and forms the inflation balloon. The tip portion, which is abuttingly affixed to the tube or body portion, is provided with a drainage lumen that must be aligned with the drainage lumen in the body of the catheter. Because of this construction, a number of problems arise both in the manufacture of the catheter and in-the use thereof. For example, as previously stated, it is desired that the pressure required to inflate a balloon should be as low as possible and thus the balloon material should be soft and relatively elastic. However, in a catheter construction of the type disclosed by Birtwell, the tip and balloon are molded as one piece and, therefore, the tip will have the same mechanical properties as the balloon. Since the tip extends longitudinally substantially beyond the end of the extruded tube, the tip may deflect and bend during insertion, i.e., the tip portion does not possess the required rigidity. Moreover, in the Birtwell construction any bending of the tip is especially deleterious because of the butt joint connection between the tip and the body, i.e., any bending of the tip will tensionally stress the bond between the tip and the body with the probable result of a failure of the bond.

Finally, because the tip in the Birtwell construction includes a drainage lumen, assembly of the tip and the tube is exacting if a misalignment is to be avoided'The problem of avoiding a misalignment during the assembly of the tip and tube is economically significant since the avoidance of such misalignment requires that one must resort to either a manual assembly or a sophisti cated mechanical assembly.

Another manufacturing difficulty associated with catheters of the type disclosed by Birtwell relates to the problems of the bond between the tip and tube. More particularly, since this bond is essentially a butt joint, an adhesive of extraordinary strength is required. Indeed, in practice, it has been found to be difficult to locate any adhesive which is sufficiently strong to withstand the stresses to which this joint is subjected. In addition, however, even if an adhesive of sufficient strength is employed, it has been found that when the adhesive sets the tip is often longitudinally misaligned with the tube. While the cause of this misalignment phenomonon is not clearly understood, it is believed that the problem may arise from either an uneven amount of adhesive being initially deposited on the tip or, alternatively, from an uneven drying or curing of the adhesive. In any event, the problem is manifest and is present almost to the point of precluding economic manufacture of such a construction.

The catheter construction disclosed hereinafter and the method of manufacture substantially overcomes all of the problems associated with prior art catheters and their method of manufacture.

SUMMARY OF THE INVENTION The improved retention type catheter comprises an extruded silicone rubber tube with a funnel secured to one end and a closed end sleeve disposed around the other end. The sleeve has a modulus of elasticity which is less than the modulus of elasticity of the tube. The tip of the closed end sleeve is substantially solid in cross section and has a rounded exterior and an interior which includes a shoulder which substantially abuts the end of the extruded tube. The sleeve is peripherally bonded to the tube so as to form a balloon section. The tube is provided with longitudinal drainage and inflation lumens, the distal portion of the inflation lumen being plugged. The outer diameter of the tube may be reduced in the area where the sleeve is bonded to the tube. Preferably, the sleeve is bonded to the tube with an uncured, catalyzed, heat curable silicone rubber. In the preferred embodiment, the tube is ground to provide a shoulder in the balloon forming region for additional strength. The bond between the tube and the sleeve may be strengthened by providing a protuberance on the interior of the tip which is received in the drainage lumen.

Also disclosed is a method of manufacturing such an improved retention type catheter which includes the step of radially compressing the tube and the sleeve during the bonding thereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of one embodiment of the instant invention.

FIG. 2 is a sectional view taken along the section line 2--2 of FIG. 1.

FIG. 3 is a sectional view taken along the section line 3-3 of FIG. 1.

FIG. 4 is a fragmentary, exploded sectional view of one part of the catheter shown in Fig. 1. FIG. 5 is a sectional view of another embodiment of the instant invention.

Fig. 6 is a view, in section, of an apparatus used in the novel method of manufacture disclosed herein.

FIG. 7 is a sectional view of another apparatus used in the practice of the method disclosed herein.

FIG. 8 is an exploded, fragmentary sectional view of one part of the catheter shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown one embodiment of a catheter construction in accordance with the invention disclosed herein. More particularly, the catheter shown in FIG. 1 includes an extruded tube 12 which, preferably,is silicone rubber. The tube 12 includes a drainage lumen 14 and an inflation lumen 15 both of which extend longitudinally for the entire length of the tube 12. The use of an extruded tube is preferred, from a manufacturing point of view, because the tube can be extruded in, essentially, an infinite length and later cut to the desired length. Of course, since the tube is continuously extruded, the tube intrinsically has a uniform diameter.

In order to manufacture a catheter of the type disclosed in FIG. 1 and in accordance with the novel method of manufacture disclosed herein, one first ob tains an extruded tube 12 which has been cut to the desired length, e. g. 17 inches. Of course, the extrusion die is sized to produce a catheter tube 12 of the desired diameter. When one has obtained an extruded tube 112 of the desired length and diameter, one end of the tube (the distal end) is reduced in diameter. Manufacturing experiments conducted upon the occasion of this invention indicate that the preferential method step for obtaining the aforementioned diameter reduction is a grinding step. Although the prior art discloses other approaches for reducing the diameter of catheter tubes, e.g., clamping under conditions of elevated pressure and temperature, it has been found that such prior art approaches do not provide the manufacturing tolerances which are required for the production of a catheter which is acceptable to both the physician and the patient. In addition, since the catheter construction disclosed herein utilizes peripheral bonding, it is desired to condition the surface of the tube, at the bonding area, so as to be receptive to the bonding agent. By utilizing a grinding process to reduce the diameter of the tube, it has been found that the peripheral surface of the tube is simultaneously conditioned so as to increase its receptivity to certain preferred bonding agents.

Referring to FIG. 1, the manufacturer of the catheter disclosed therein would thus proceed by grinding the tube 12 in the areas 16 and 20. Preferentially, the diameter of the tube 12 in the areas 16 and 20 is reduced by an amount which is slightly greater than twice the thickness of a sleeve which is subsequently disposed about the distal end of the tube.

A close inspection of the catheter construction disclosed in FIG. 1 will reveal that the diameter of the extruded tube 12 has been reduced in the areas 16 and 20 but not in the area or region 18. Thus, in the construction disclosed in FIG. I. the'two reduced areas 16 and 20 define an annular shoulder in the region or area 18. Although it is within the scope of this invention to reduce the outer diameter of the tube 12 over the entire distal end of the tube, it is preferred to reduce the diameter in two separate areas so as to provide the aforementioned annular shoulder which is included to increase the strength and rigidity of the distal end of the tube 12.

Continuing with the manufacturing process, after the outer diameter of the tube 12 has been reduced in the regions 16 and 18, a first radial aperture 25 is provided in the wall of the tube 12 and communicates with the inflation lumen 15. Subsequently, an adhesive is deposited around the periphery of the tube in the regions wherein the diameter of the tube 12 has been reduced. Through experiments, it has been found that certain adhesives are clearly superior in terms of providing the required bonding strength while simultaneously facilitating the process of manufacture. More particularly, it has been found that uncured, heat curable silicone rubher is especially effective although so called room tempcrature vulcanizing silicone rubber may also be employed.

Either before or after the boding agent has been deposited on the tube as described above, the inflation lumen at the distal end of the tube 12 is filled or plugged with a material 32. The purpose of filling or plugging the distal end of the inflation lumen l5 will be described hereinafter. Thus at this point, suffice it to say that the plugging of the distal end of the inflation lumen 15 may be advantageously achieved by filling the distal end of the inflation lumen 15 with an uncured, catalyzed silicone rubber ofthe type preferentially employed as the bonding agent.

After the extruded tube 12 is subjected to the manufacturing processes described above, a closed end sleeve 21 is disposed about the distal end of the tube. Since the closed end sleeve 21 is the part of the catheter which initially contacts the patient and thus acts somewhat as a guide, its construction, mechanical properties and method of fabrication are critical. For example, the sleeve 21 should be fabricated in a manner such that no seams or joints are created. Additionally, all of the dimensions associated with the sleeve must be maintained within a close tolerance. For example, the over-all length of the sleeve should be such that the rear or proximal edge of the sleeve terminates close to the proximal end of the region 16. If the sleeve were to extend past the reduced diameter region 16, the smooth exterior of the catheter would be destroyed and substantial patient discomfort would result. Similarly, it will be evident that the diameter of the sleeve must be maintained within a rather close tolerance if the sleeve is to be effectively bonded to the tube 12. In view of these factors, it has been determined that a superior method for manufacturing such a closed end sleeve is to employ a vertical, fiashless molding technique. Referring to FIG. 6, a two-piece vertical mold may be employed. In operation, a quantity of uncured silicone rubber is deposited in the bottom of the cavity of the female mold 50. Subsequently, the male mold 51' is positioned within the female mold and the molds 50, 51 are heated. At the bottom of the cavity in the female mold 50, a discharge conduit 52 is provided so that air and excessive material within the cavity may be displaced. Preferably, the male mold 51 is provided with a plurality of guide pins 55 which serve to accurately position the downwardly depending section of the male mold with respect to the cavity in the female mold 50. In practice, hydraulic or pneumatic cylinders are generally employed to press together the male and female molds 50, 51 and to maintain them in their closed position while the combination is heated. As a result of these steps, a flashless, closed end sleeve is formed about the downwardly depending section of the male mold 51. During the curing or partial curing of the closed end sleeve, the sleeve tends to shrink around the depending section of the male mold 51, thus facilitating removal of the male mold 51. After the mold S1 is removed, the closed end sleeve is rolled off of the extending section of the mold 51.

While a number of materials such as silicone rubber may be used to form the closed end sleeve 21, it is critical to this invention that the modulus of elasticity of the sleeve be less than the modulus of elasticity of the tube. Stated otherwise, we have discovered that a superior urinary catheter results when two conditions are satisfled, viz: (1) when the catheter tube or shaft extends almost to the distal end of the catheter; and (2) the distal end of the catheter is covered by a closed end sleeve having a modulus of elasticity which is less than the modulus of elasticity of the shaft. The following reasons appear to explain why this new combination is superior. First, by insuring that the modulus of elasticity of the sleeve is low, one insures that (l) the tip of the sleeve will be soft (which promotes patient comfort) and (2) the pressure required to inflate the balloon is minimized. Second, by insuring that the modulus of elasticity of the shaft is relatively high, it has been found that bending of the shaft to the point that the lumens are occluded is substantially reduced or eliminated. Additionally, by employing a shaft with a high modulus of elasticity, the wall thickness of both the inflation lumen and the drainage lumen may be minimized, thus maximizing the crosssectional area of the drainage lumen. With respect to the prevention of bending, it is now believed that the benefit of using a shaft material having a high modulus of elasticity can be understood by viewing the catheter shaft as a column which, in use, should not buckle. A commonly used formula to determine the load at which a column will buckle indicates that the buckling load is proportional to the modulus of elasticity. Thus, by using a material for the shaft which has a high modulus of elasticity, buckling or bending of the catheter is minimized or prevented.

When the closed end sleeve is unrolled from the depending section of the male mold shown in FIG. 6, it may then be combined with the tube 12 which has been subjected to the manufacturing step set forth above, i.e. the tube diameter has been reduced at the distal end, a first radial aperture 25 has been provided, the distal end of the inflation lumen has been sealed or plugged and two bands of bonding agents or adhesives have been deposited around the tube. Thus, the closed end sleeve 21 may be unrolled onto the tube 12. When the closed end sleeve 21 is thus positioned around the tube 12, the combination is, according to the preferred embodiment of this invention, inserted within a mold of the type shown in. FIG. 7. Referring to FIG. 7, there is provided a mold 70 having a cavity which substantially corresponds in cross section to the distal end of the catheter. The mold 70 is seperable at the transverse parting line 99. To insert the catheter, the top part of the mold is removed, the catheter is inserted and the top of the mold is replaced. The two halves of the mold may be held together, if necessary, by any convenient means. In order to facilitate insertion of the catheter into the mold, it is preferable to induce a partial vacuum within the catheter and thereby slightly reduce its outer diameter. When the catheter, generally referred to in FIG. 7 as 29, has been thus positioned within the mold 70, a pressurizing source 71, e.g., a hypodermic needle or an air supply, is inserted in the drainage lumen at the proximal end of the catheter 29. Using the pressurizing source 71, the pressure within the drainage lumen 29 is increased. Since the mold 70 snugly surrounds the distal end of the catheter 29, it will be seen that by pressurizing the drainage lumen 14, the tube 12 and the closed end sleeve 21 are radially compressed. If a room temperature vulcanizing agent or another adhesive is used which does not require heat, such radial compression is maintained while a peripheral bond is formed between the tube 12 and the closed end sleeve 21. Alternatively, if a heat activated adhesive or bonding agent is used, the mold 70 may advantageously be provided with a heating element 72 which is externally connected to an electric current source. Obviously, other means may be used to heat the mold 70, e.g., induction heating or immersion in a heated bath. In any event, the important process step reflected by FIG. 7 resides in radially compressing the tube 12 and the closed end sleeve 21 so that a strong bond is formed while, simultaneously, a smooth and continuous exterior is insured. For example, referring again to FIG. 1, it may be noted that the closed end sleeve 21 tenninates at a point which is slightly distant from the end of the reduced diameter region 16. However, as shown in FIG. 1, the annulus 30 is filled with an adhesive or a bonding agent in order to thus provide a smooth exterior contour and also a smooth transition from the balloon to the shaft. Such a smooth contouris substantially insured and promoted by the process step of radially compressing the tube 12 in the closed end sleeve 21 as shown in FIG. 7.

A significant structural advantage intrinsically occurs when the novel catheter construction of FIG. l-is subjected to the radial compression step illustrated in FIG. 7. More particularly, it will be recalled that the tube 12 as shown in FIG. 1 was ground in the region 16 and 20 so as to produce an annular shoulder 18. Referring to FIG. 4, the intrinsic benefit of providing the annular shoulder 18 arises from the fact that the shoulder will function as a barrier to prevent the longitudinal flow of adhesive or bonding agent. Thus, referring to FIG. 4, it may be noted that a quantity of adhesive or bonding agent has accumulated at the point 31. The accumulation of the adesive at the point 31 occurred during the step of radially compressing the sleeve 21 and the tube 12. The adhesive or bonding agent which accumulated at the point or annulus 31 represents excess adhesive which would be pressed into the balloon area in the absence of the shoulder in the region 18. Thus, the shoulder in the region 18 provides a reservoir for receiving excess adhesive and preventing such excess adhesive or bonding agent from flowing into the balloon area. Similarly, FIG. 4 clearly illustrates that the annulus formed by the terminal portion 21A of the closed sleeve 21 and the rearward edge of the reduced diameter area 16 is automatically filled and contoured by virtue of the process of radially compressing the closed end sleeve 21 and the tube 12.

Returning to a consideration of the function of the annular shoulder in-the region 12, it is especially desirable to prevent longitudinal flow of the adhesive or bonding agent into the balloon area since, if any such local longitudinal flow should occur, the ballon would, upon inflation, be skewed, i.e. a uniform annular balloon would not be formed. Such a distortion of the balloon could severely impair the effective use of the catheter and is thus avoided by the presence of the annular shoulder in the region 18.

After the catheter is removed from the mold as shown in FIG. 7, a second radial aperture 24 is provided in the distal end of the catheter 29 as shown in FIG. 1. The aperture 24 is preferably provided completely through the catheter 29 as most clearly shown in FIG. 2. As will be evident from a consideration of FIG. 2, the second aperture 24 communicates with the drainage lumen 14 and thus provides the required drainage path. With further regard to FIG. 2, it will be noted the size of the aperture 24 is such that the edge of the aperture 24 is tangent to the plugs 32. Thus, it will be appreciated that if the plug 32 was not provided in the distal end of the inflation lumen, the drainage aperture 24 might intercept the inflation lumen and thus destroy the inflatability of the catheter. Such a possibih ity is particularly evident when one considers the normal cross-section of the catheter tube 12 as shown in FIG. 3. Indeed, considering the cross section of the tube as shown in FIG. 3, it will be appreciated that if a drainage aperture of a size shown in FIG. 2 is eniployed and is randomly located, the probability is that the drainage aperture will intercept the inflation lumen 15. Thus, the plugging or sealing of the drainage lumen 15, as previously described, greatly facilitates the manufacture of a catheter of the type shown in FIG. 1.

After the second radial aperture 24 has been provided, the completed catheter may be post cured, i.e. it has been found that a superior construction is obtained if the extruded shaft and the closed end sleeve are, initially, only partially cured. Thus, if a partially cured tube and sleeve are used, the final construction must then be cured (post curing). The length of the post cure is sufficient to permanently set the material and drive off any residual catalyst.

While certain structural advantages-of the catheter shown in FIG. I have previously been described, other structural advantages exist which are not evident from considering only the manufacturing process for fabrieating such a catheter. For example, referring to FIG. 1, it may be noted that the closed end sleeve 21 includes a substantially solid tip 23 having a rounded exterior and an interior which includes the shoulder 27. As shown in FIG. I, tip 23 may be provided with a centrally disposed cavity 26 to receive a stylet. If the tip 23 is provided with a stylet receiving cavity as shown in FIG. 1, the shoulder 27 will be annular, as shown. In any event, it will be appreciated that the word shoulder, as used herein, means a substantially flat, transverse portion of the tip which abuts the distal, transverse end of the shaft.

Because the tip portion 23 of the closed end sleeve 21 is substantially solid, and because of the presence of the annular shoulder 27, a catheter construction results which avoids many of the problems associated with prior art catheter constructions notwithstanding the fact that there is a similarity between the materials used in the catheter construction of FIG. I and the materials employed in prior art catheters. For example, it may be noted that in the embodiment of FIG. 1, the cavity 26 is of a diameter which is less than the maximum diameter of the drainage lumen. Thus, the annular shoulder 27 abuts the transverse end of the tube I2. Because of the presence of the annular shoulder 27 which abuts the transverse end of the tube 32 and because the tip 23 is substantially solid, the tip 23 is significantly more rigid than the tips of prior art catheters wherein drainage lumens were formed in the tip. Thus, this particular construction avoids the problem which prior art catheters encountered, i.e. the problem of the tip bending or deflecting during insertion. Additionally, because of the closed end sleeve is peripherally bonded to the tube, a butt joint connection is not relied upon and a stronger and more dependable structure results. Preferably, however, the tip 23 is at least partially bonded to the tube 12 when a right angular type annular shoulder of the type shown in FIG. 1 is employed. At least a partial butt joint connection between the shaft and the tip is desirable so that if a stylet is used to insert the catheter, the force exerted by the stylet will not be exclusively carried by the sleeve but will be carried by both the sleeve and the butt joint.

Although the catheter construction shown in FIG. 1 has been found to be satisfactory for most applications, it may be desirable under certain circumstances to provide a catheter with a greater bonding area and somewhat greater tip to shaft rigidity. These objectives can be achieved by using the embodiment shown in FIGS. 5 and 8 wherein two modifications are simultaneously FIGS. 5 and 8 are embodied in a single catheter, it will be understood that either may be used alone.

The first modification resides in providing'a protu berance 37 on the interior of the tip 23. At the center of the protuberance 37 there may be located a cavity 26 for receiving a stylet. If the cavity 26 is provided, the protuberance 37 will be annular as shown in FIGS. 5 and 8. The protuberance 37 is arranged on the tip and sized so as to be engagingly received within the drainage lumen 14 of the extruded tube 12.

More particuarly, it will be apparent that since the interior of the tip is symmetrical, a small interference will occur between the tip and shaft in the region of the inflation lumen, i.e. the inner wall of the inflation lumen may interfere with one section of the protuberance. However, this small interference generally will not cause any difficulty during assembly because the inner wall of the inflation lumen is relatively thin and easily deformable and preferably the shaft and the sleeve are assembled while in a semi-cured condition. The deformation which may arise during assembly is evident in FIGS. 5 and 8, for example as shown at 60. While the resulting deformation may initially disturb the exterior concentricity of the catheter tip, the subsequent post curing of the distal end of the catheter, e.g. as shown in FIG. 7, will insure that the exterior of the catheter is concentric and smoothly contoured.

The embodiment of our invention which includes a protuberance as shown in FIGS. 5 and 8 is particularly advantageous because an increased bonding area between the tip and the shaft is thus provided which consequently provides a greater tip to shaft rigidity. Thus, in FIGS. 5 and 8, it will be seen that adhesive 61 is provided between the interior of the shaft walls and the longitudinal sides of the protuberance 37. Additionally, it has been found that providing a protuberance which is received in the drainage lumen 14 facilitates the correct positioning of the closed end sleeve 21 on the tube 12 prior to unrolling the sleeve.

Another advantage of the tip construction shown in FIGS. 5 and 8 is the fact that the protuberance 37 and a portion of the tip 23 may be provided separately from the sleeve 21. For example, the phantom line 28 in FIG. 8 indicates that the sleeve 21 may be of essentially constant thickness and disposed over the tip 23. Thus, the substantially solid portion of the tip 23 does not have to be integral with the sleeve 21. In certain instances, such a non-integral construction may be desirable. For example, it may be desirable to construct a catheter wherein the tip is comprises of a material which is different than the sleeve material or the shaft material.

- Such a situation might arise when it is desired to locate employed. Although the two modifications shown in the tip of the catheter, within a patient. by the use of x-rays. Such an objective could be readily achieved if the catheter included a non-integral tip comprised of a material which was radio opaque. Obviously, a radio opaque material, i.e. a material containing a barium salt, may not be a material which one would desire to directly contact the patient. By employing a nonintegral tip construction, such undesirable direct contact may then be avoided.

The second modification shown in FIGS. 5 and 8 is the chamfer or bevel 45 at the distal end of the shaft 12. The benefit of this modification relates to the directional orientation of the stresses to which the tip-shaft combination are subjected. Thus, by providing the peripheral bevel 45, the butt joint bonding area between the tip and the shaft is reduced and replaced by the bevel bonding surface 45. As a result, the unity and strength of the tip-shaft combination is improved.

As is well known to those skilled in the art, retention catheters are generally supplied with a funnel at their proximal end. For example, Birtwell discloses a dual funnel which may be bonded to the proximal end of an extruded catheter shaft. Since the need for and use of such a dual funnel is known to those skilled in the art, a discussion thereof is not included herein, it being understood that as used herein, the phrase retention catheter includes a funnel or funnels of appropriate design at the proximal end.

While certain preferrred embodiments of the instant invention have hereinbefore been recited, it will be appreciated that such embodiments are presented by way of example and other embodiments of this invention may be perceived by those skilled in the art without dcparting from the scope of the invention as defined by the claims appended hereto.

We claim:

I. A retention catheter which comprises:

a. an extruded tube having a drainage lumen extending longitudinally for the entire length thereof, an inflation lumen extending longitudinally for the entire length thereof, a first radial aperture in the wall of said tube adjacent the distal end thereof communicating with said drainage lumen and a second radial aperture in the wall of said tube, adjacent the distal end thereof but proximally located with respect to said first aperture and communicating with said inflation lumen;

b. means for plugging said inflation lumen distally of said second aperture;

c. a closed end sleeve, having a modulus of elasticity less than the modulus of elasticity of said tube, disposed around the distal end of said tube and extending proximally along said tube to a point past said second aperture and having an aperture aligned with said first aperture, the tip of said sleeve being substantially solid and having a rounded exterior and an interior which includes a shoulder which substantially abuts the transverse distal end of said tube, said closed end sleeve peripherally and at least, in part, abuttingly bonded to said tube, the area of peripheral bonding between said tube and said shaft defining two bands with an unbonded area therebetween, said unbonded area including said second aperture.

2. The catheter of claim 1 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.

3. The catheter of claim 2 wherein said tube further includes an annular shoulder in said unbonded area.

4. The catheter of claim 1 wherein the distal end of said tube is beveled.

S. The catheter of claim 4 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.

6. The catheter of claim 5 wherein said tube further includes an annular shoulder in said unbonded area.

7. The catheter of claim 1 which further includes a protuberance, integral with said tip and extending into and engagingly received by said inflation lumen.

8. The catheter of claim 7 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.

9. The catheter of claim 8 wherein said tube further includes an annular shoulder in said unbonded area.

10. The catheter of claim 9 wherein the distal end of said tube is beveled.

11. A retention catheter which comprises:

a. an extruded tube having a drainage lumen extending longitudinally for the entire length thereof, an inflation lumen extending longitudinally for the entire length thereof, a first radial aperture in the wall of said tube adjacent the distal end thereof communicating with said drainage lumen and a second radial aperture in the wall of said tube, adjacent the distal end thereof but proximally located with respect to said first aperture and communicating with said inflation lumen;

b. means for plugging said inflation lumen distally of said second aperture;

c. a substantially solid tip bonded to the distal end of said tube, said tip having,

i. a rearwardly extending protuberance engagingly received in said drainage lumen,

ii. an annular shoulder substantially abutting the transverse end of said tube, and

iii. a rounded, forward exterior;

d. a closed end sleeve, having a modulus of elasticity less than the modulus of elasticity of said tube, disposed around said tip and the distal end of said tube and extending proximally along said tube to a point past said second aperture and having an aperture aligned with said first aperture, said closed end sleeve peripherally bonded to said tube and said tip, the area of peripheral bonding between said tube and said shaft defining two bands with an unbonded area therebetween, said unbonded area including said second aperture.

12. The catheter of claim 11 wherein said tip is radio opaque.

13. The method of manufacturing a retention catheter which comprises:

a. providing an extruded tube having a drainage lumen extending longitudinally for the entire length thereof and an inflation lumen extending longitudinally for the entire length thereof;

b. providing a first aperture through said tube, at one end thereof, communicating with said inflation lumen;

c. plugging said inflation lumen on the distal side of said first aperture;

d. molding a closed end sleeve;

e. depositing a band of bonding material around said tube on the distal side of said first aperture;

f. depositiing a band of bonding material around said tube on the proximal side of said first aperture;

g. mounting said sleeve on said tube at said one end;

h. bonding said tube to said sleeve while simultaneously radially compressing said tube and said sleeve; and

. providing a second aperture through said tube and said sleeve at a point between said first aperture and said one end of said tube, said second aperture communicating with said drainage lumen.

16. The method of claim 15 wherein said bonding and compressing'step includes the steps of:

a. positioning the tube and sleeve within a cavity which engagingly surrounds said sleeve; and b. increasing the pressure within said drainage lumen.

17. The method of claim 16 wherein said tube, said sleeve and said bonding material are silicone rubber.

18. The method of claim 17 wherein said tube and said sleeve are partially cured silicone rubber and further including the step of post curing said tube and sleeve after providing said second aperture. 

1. A retention catheter which comprises: a. an extruded tube having a drainage lumen extending longitudinally for the entire length thereof, an inflation lumen extending longitudinally for the entire length thereof, a first radial aperture in the wall of said tube adjacent the distal end thereof communicating with said drainage lumen and a second radial aperture in the wall of said tube, adjacent the distal end thereof but proximally located with respect to said first aperture and communicating with said inflation lumen; b. means for plugging said inflation lumen distally of said second aperture; c. a closed end sleeve, having a modulus of elasticity less than the modulus of elasticity of said tube, disposed around the distal end of said tube and extending proximally along said tube to a point past said second aperture and having an aperture aligned with said first aperture, the tip of said sleeve being substantially solid and having a rounded exterior and an interior which includes a shoulder which substantially abuts the transverse distal end of said tube, said closed end sleeve peripherally and at least, in part, abuttingly bonded to said tube, the area of peripheral bonding between said tube and said shaft defining two bands with an unbonded area therebetween, said unbonded area including said second aperture.
 2. The catheter of claim 1 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.
 3. The catheter of claim 2 wherein said tube further includes an annular shoulder in said unbonded area.
 4. The catheter of claim 1 wherein the distal end of said tube is beveled.
 5. The catheter of claim 4 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.
 6. The catheter of claim 5 wherein said tube further includes an annular shoulder in said unbonded area.
 7. The catheter of claim 1 which further includes a protuberance, integral with said tip and extending into and engagingly received by said inflation lumen.
 8. The catheter of claim 7 wherein the diameter of the distal end of said tube is reduced in the region where said tube is peripherally bonded to said sleeve.
 9. The catheter of claim 8 wherein said tube further includes an annular shoulder in said unbonded area.
 10. The catheter of claim 9 wherein the distal end of said tube is beveled.
 11. A retention catheter which comprises: a. an extruded tube having a drainage lumen extending longitudinally for the entire length thereof, an inflation lumen extending longitudinally for the entire length thereof, a first radial aperture in the wall of said tube adjacent the distal end thereof communicating with said drainage lumen and a second radial aperture in the wall of said tube, adjacent the distal end thereof but proximally located with respect to said first aperture and communicating with said inflation lumen; b. means for plugging said inflation lumen distally of said second aperture; c. a substantially solid tip bonded to the distal end of said tube, said tip having, i. a rearwardly extending protuberance engagingly received in said drainage lumen, ii. an annular shoulder substantially abutting the transverse end of said tube, and iii. a rounded, forward exterior; d. a closed end sleeve, having a modulus of elasticity less than the modulus of elasticity of said tube, disposed around said tip and the distal end of said tube and extending proximally along said tube to a point past said second aperture and having an aperture aligned with said first aperture, said closed end sleeve peripherally bonded to said tube and said tip, the area of peripheral bonding between said tube and said shaft defining two bands with an unbonded area therebetween, said unbonded area including said second aperture.
 12. The catheter of claim 11 wherein said tip is radio opaque.
 13. The method of manufacturing a retention catheter which comprises: a. providing an extruded tube having a drainage lumen extending longitudinally for the entire length thereof and an inflation lumen extending longitudinally for the entire length thereof; b. providing a first aperture through said tube, at one end thereof, communicating with said inflation lumen; c. plugging said inflation lumen on the distal side of said first aperture; d. molding a closed end sleeve; e. depositing a band of bonding material around said tube on the distal side of said first aperture; f. depositiing a band of bonding material around said tube on the proximal side of said first aperture; g. mounting said sleeve on said tube at said one end; h. bonding said tube to said sleeve while simultaneously radially compressing said tube and said sleeve; and i. providing a second aperture through said tube and said sleeve at a point between said first aperture and said one end of said tube, said second aperture communicating with said drainage lumen.
 14. The method of claim 13 which further includes the step of heating said sleeve and said tube while said sleeve and said tube are compressed.
 15. The method of claim 14 which further includes grinding said tube at said one end to reduce the diameter thereof before said sleeve is mounted on said tube.
 16. The method of claim 15 wherein said bonding and compressing step includes the steps of: a. positioning the tube and sleeve within a cavity which engagingly surrounds said sleeve; and b. increasing the pressure within said drainage lumen.
 17. The method of claim 16 wherein said tube, said sleeve and said bonding material are silicone rubber.
 18. The method of claim 17 wherein said tube and said sleeve are partially cured silicone rubber and further including the step of post curing said tube and sleeve after providing said second aperture. 